1. Field of the Invention
The present invention relates to a thermal printer capable of printing images simultaneously on both sides of a printing medium and a drive control method of a thermal head of the thermal printer.
2. Description of the Related Art
A thermal printer capable of printing images simultaneously on both sides of a thermal paper is disclosed in Jpn. Pat. Appln. Publication No. 11-286147. This printer has two platen rollers and two thermal heads.
In this thermal printer, first and second platen rollers are rotated in synchronization with each other and at the same paper-feeding speed. The thermal paper is passed between the first platen roller and first thermal head and thereby images are printed on one side of the thermal paper by the first thermal head. The same thermal paper is then passed between the second platen roller and second thermal head and thereby images are printed on the other side of the thermal paper by the second thermal head.
As a print head used in this thermal printer, there is known a line thermal head in which a large number of heater elements are arranged in a line in the direction perpendicular to the feeding direction of the thermal paper. When a current is applied to the heater elements corresponding to recording pixels, that is, electric energy is applied, the energized heater elements generate heat. As a result, an arbitrary dot pattern is printed on the thermal paper.